Abstract

A historical cohort study was carried out in an agricultural research institute in the Republic of Ireland to investigate a perceived excess of cancer deaths among employees. The objectives of the study were (a) to confirm whether or not total or cause specific death rates among selected employees were higher than expected based on national figures, and to quantify any excess, and (b) to identify centres and employee grades associated with any excess risk. The cohort comprised all administrative, research, and technical staff employed for at least two years between 1960 and 1980, giving a final total for analysis of 1323 employees. Employment history was categorised by place of work and employment grade. Deaths among the cohort were identified and causes of deaths verified. Overall the cohort had a lower than expected mortality compared with national rates (O/E = 0.67). Female deaths were too few for analysis but, among the male employees, there was an excess of all cancers (O/E = 1.24; 95% confidence interval (95% CI) 0.8-1.9), in particular brain cancer (O/E = 4.69; 95% CI 1.2-11.4) and bladder cancer (O/E = 9.31, 95% CI 1.9-27.2). The pattern of brain tumour deaths was consistent with an occupational aetiology but it was not possible to identify specific exposures associated with the excess. All four cases occurred among research workers in the plant and soil science area. The pattern of bladder cancers was difficult to interpret. The authors are at present participating in a multicentre study to further investigate cancer risk in laboratory workers.